1. Field of the Invention
The present invention relates to a pattern evaluation method, a computer-readable recording medium, and a manufacturing method of a semiconductor device.
2. Related Background Art
A method of detecting an edge of an evaluation pattern to evaluate a shape of the pattern is extensively adopted in various industrial fields. For example, in manufacture a semiconductor device, accurately measuring a fine pattern formed by, e.g., a photolithography process, a film forming process, or an etching process is required to manufacture a fine device with an excellent yield ratio. CD measurement using a CDSEM (Critical Dimension Scanning Electron Microscope) has been conventionally extensively carried out as pattern measurement.
In recent years, to satisfy demands for realization of high performances or high functions of devices, not only sizes of patterns are miniaturized but also shapes of the same are becoming more complicated. To evaluate each of these patterns having complicated shapes, a shape of the entire pattern must be measured as different from the conventional CD measurement that measures a specific part of the pattern. For example, a technique of superimposing a design pattern obtained based on design data on an evaluation pattern to measure a difference between these patterns has been already carried out. However, as different from general industrial products, a pattern shape of a semiconductor device often greatly deviates from design data. In particular, since a corner part of the pattern is apt to be affected by an optical resolution of a pattern exposure device, forming such a right-angle part as that in the design pattern is difficult, and a rounded shape is generally obtained. Therefore, when measuring a difference in shape between an evaluation pattern and a design pattern, an influence of a corner part on a size is different from that of any other part on the same. The number of the corner parts in the pattern varies depending on complexity of the pattern, and hence a magnitude of the different is dependent on complexity of the pattern. This means that using the difference between the evaluation pattern and the design pattern is inappropriate to evaluate, e.g., a line pattern or a pattern in which line patterns are intricately coupled by using the same index. Therefore, corner parts of the pattern must be excluded from measurement of the difference when measuring the difference.
Here, achieving the above-explained object is not impossible by specifying a range of a specific part (the corner part) based on an operator's assist, but extracting each corner part of an actually formed semiconductor pattern by using human eyes is difficult as different from design data consisting of straight lines. Therefore, not only an accurate result cannot be obtained, but also a problem that a large individual difference occurs in accordance with a proficiency degree of each operator arises. Therefore, there can be also considered, e.g., an automation technique of using an image processing technology based on a computer to detect an edge of a pattern, calculating a local curvature thereof, and separating linear parts and corner parts in the pattern based on this curvature, thereby requiring no assist of an operator (Japanese patent laid open (kokai) 2005-098885).
However, according to the above-explained technique, if even a part of a pattern that should be evaluated as a linear part under normal conditions is deformed due to various processes, e.g., exposure conditions and a curvature is thereby locally increased, there can be considered a case that a contribution as a corner part to its difference is eliminated. Further, when exposure conditions are intentionally exerted at predetermined intervals to evaluate a pattern, since a pattern deformation degree differs in accordance with each pattern, a proportion of linear parts in a pattern edge differs between a largely-deformed pattern and a less-deformed pattern in the above-explained automation technique. As a result, there occurs a problem that using the difference as an evaluation index for a pattern deformation degree is difficult.